[ash-md] Added different highlighting modes to the InkDropImpl.

ui/views/controls/combobox/combobox.cc

Index: ui/views/controls/combobox/combobox.cc
diff --git a/ui/views/controls/combobox/combobox.cc b/ui/views/controls/combobox/combobox.cc
index 6f54c920d22ca2065a14c272e297a6e2b2b13f51..0211398eb06d1dfb95d235a3bb3685bcc641834d 100644
--- a/ui/views/controls/combobox/combobox.cc
+++ b/ui/views/controls/combobox/combobox.cc
@@ -30,6 +30,7 @@
 #include "ui/resources/grit/ui_resources.h"
 #include "ui/views/animation/flood_fill_ink_drop_ripple.h"
 #include "ui/views/animation/ink_drop_highlight.h"
+#include "ui/views/animation/ink_drop_impl.h"
 #include "ui/views/background.h"
 #include "ui/views/controls/button/custom_button.h"
 #include "ui/views/controls/button/label_button.h"
@@ -150,10 +151,6 @@ class TransparentButton : public CustomButton {
             ink_drop_visible_opacity()));
   }
 
-  std::unique_ptr<InkDropHighlight> CreateInkDropHighlight() const override {
-    return nullptr;
-  }
-
  private:
   DISALLOW_COPY_AND_ASSIGN(TransparentButton);
 };